Characterization of central- and peripheral-type benzodiazepine receptors in rat salivary glands.

Benzodiazepines have been shown to inhibit salivary secretion from the rat salivary gland. This action is mediated by specific benzodiazepine binding sites in the glands. The presence and characteristics of central- and peripheral-type benzodiazepine receptors in rat parotid and submandibular glands were examined employing [3H]Ro15-1788 and [3H]PK11195 as radioligands. [3H]Ro15-1788 and [3H]PK11195 bound with high affinity for both salivary glands ([3H]Ro15-1788: 24.5 and 37.4 mM, [3H]PK11195: 1.37 and 1.88 nM, for parotid and submandibular glands, respectively). [3H]Ro15-1788 binding sites occupied only 0.22 to 0.43% of the total binding for benzodiazepine receptors in the glands. The rank order of the competing potency of [3H]Ro15-1788 binding (Ro15-1788 = clonazepam > diazepam > flunitrazepam > PK11195 > Ro5-4864) and [3H]PK11195 binding (Ro5-4864 = PK11195 > diazepam = flunitrazepam > clonazepam) demonstrated that [3H]Ro15-1788 and [3H]PK11195 binding sites were characteristic of the central and peripheral type, respectively. These studies show that both central- and peripheral-type benzodiazepine receptors exist in rat parotid and submandibular glands.